Apparatus for generating high energy gaseous blast

ABSTRACT

A gas burner comprising a metallic housing for receiving a premix of fuel and air for introduction into a combustion chamber enclosed thereby. Metallic, gas permeable walls form the combustion chamber wherein the premix of fuel and air is burned producing a high temperative effluent which is directed by a metallic converging slot nozzle to an outlet which shapes the effluent while its velocity is increased by the nozzle to form a high temperature, wide, flat stream of uniform velocity and temperature which is an effective filament attenuator for materials such as glass.

United States Patent 1 1 Shisler [451 May 29, 1973 [54] APPARATUS FOR GENERATING HIGH ENERGY GASEOUS BLAST Primary Examiner-Edward G. Favors Att0rney.lohn A. McKinney, Robert M. Krone, [75] Inventor. goliiigld Eugene Shisler, Napoleon, Joseph J. Kelly and RonaldM'Halvorsen [73] Assignee: Johns Manville Corporation, New [57] ABSTRACT York A gas burner comprising a metallic housing for receiv- [22] Filed: June 1, 1971 ing a premix of fuel and air for introduction into a combustion chamber enclosed thereby. Metallic, gas [21] Appl' permeable walls form the combustion chamber 7 wherein the premix of fuel and air is burned producing [52] U.S.Cl ..43l/158 a g temperative fluent whi h is directed by a 51 Int. Cl ..F23r 1/02 metallic converging Slot nozzle to an Outlet which [58] Field of Search ..431 /l58, 170, 326, Shapes the effluent while its velocity is increased y 431 7 the nozzle to form a high temperature, wide, flat 4 stream of uniform velocity and temperature which is 5 References Cited an effective filament attenuator for materials such as glass. UNITED STATES PATENTS 23 Claims, 7 Drawing Figures 3,045,278 7/1962 Potter ..43l/l58 X 3,322,180 5/1967 Perrym, ..431/l58 7/1958 Piolenc et al ..43l/l58 as 83 56 r 76 82 I I I ll l s ,1

Ll] 1 46 N 78 72 V 4 \44 4 74 94 M 36 j 1 f 4: 92 I24 4 56 4s 3 APPARATUS FOR GENERATING HIGH ENERGY GASEOUS BLAST BACKGROUND OF THE INVENTION In the art of gaseous heating there are burners which generate a high energy stream of products of combustion having high temperature and high velocity. Such burners are employed, for example, in the process of attenuating primary filaments of glass to glass wool fibers. Refractory combustion chambers have been used in these high energy burners to stabilize the flame with the refractories often used as ignitors for the fuel burned. The refractories give rise to two problems, a short burner life due to erosion of the refractories and a decrease in velocity of the exiting gases or products of combustion due to friction between the refractories and the gases.

There are applications which require high energy burners, of the above type, to develop a wide flat blast of heating gases in the local heating of work which is being continuously advanced in planar array in relation to the blast such as in flame hardening and flame drawing of attenuating processes. To increase the rate of production of heating gases, often times a premix fuel is used to accelerate the combustion process. Problems associated with the use of such fuels include flash back (backfire), and blow off (isolation of the flame from the emitting port). Where the above problems associated with premix fuel have been overcome, the required equipment to do so has been elaborate such as multiple ported manifolds with substantial length between combustion chamber outlet and fuel inlet of the manifold which often was exposed to ambient for required cooling to prevent flash back and long refractory throats to prevent blow off. The long refractory throats also served to prevent flame emission from the outlet of the burner and provided for completion of combustion where necessary together with the shaping of the fluid flow leaving the burner.

The shape or configuration of the fluid flow leaving the burner is particularly important where the burner is used for flame attenuating glass filaments wherein a uniform blast of generally laminar flow is desirable. Further, combustion should be completed within the burner to assure a uniform glass product of high quality. The prior art refractory tunnel burners, while providing for shaping and complete combustion, had the problems associated with refractory materials described above of erosion and slowing of the exiting heating gases.

In addition, the wide slot type outlet required to produce the desired flat blast of heating gases was found to be a difficult shape to maintain with refractory materials. Expansion of the refractory materials at the outlet of the burner, upon being heated by the heating gases emitting therefrom, caused bowing of the refractory which tended to close off the outlet. After a number of cycles of heating the outlet and subsequent cooling to ambient the refractories would deteriorate. Normal life span for the refractory outlet was found to be 30 to 45 days. Other attempts at producing an all metal burner to overcome the deficiencies found in burners using refractories have proved entirely unsatisfactory when placed on a facility for attenuating glass filaments. The burners did not produce the requisite high energy stream of effluent with associated force to attenuate the filament. A bushy flame was produced which ex- SUMMARY This invention relates to burners for generating high energy gaseous blasts and more particularly to burners which generate a high energy stream or blast by buming a premix consisting of a mixture of fuel and air and which shape the eflluent or heating gases resulting from burning premix as it is emitted from the burner. The products formed as above and the stream they constitute are uniform in temperature and velocity over the face of the outlet to produce a uniform stream for doing work.

In one embodiment of the present apparatus, the burner is used to attenuate glass filaments into fibers which is a process requiring a high degree of uniformity in temperature and force of the stream attenuating the fibers to produce a uniform product. A satisfactory stream has been produced using a metallic housing or combustor to form a combustion chamber for the buming of a premix of fuel and air. Encompassing all but an opening in the combustor is a mild steel casing forming a plenum with means for supplying a fuel and air mixture and for establishing a uniform pressure of premix around the combustor. The combustor outlet port at a side of the plenum, allows the products of combustion to discharge to a metallic nozzle adjacent the outlet port. In the embodiment illustrated a refractory chamber encased in mild steel is inserted in between the combustor and nozzle to provide a secondary combustion chamber for the completion of combustion started within the combustor when the range of fuel inputs desired exceeds the capabilities of the combustor. The

nozzle shapes the products emitting from the burner outlet to conform to the shape of the outlet.

The combustor in the preferred embodiment has opposing permeable planar surfaces forming opposite major walls of the combustion chamber, a back plate and two end plates. An example of material for the permeable planar surfaces is perforated plate. Indentation of the back plate provides for distribution and preheating of the premix upon discharge from the inlet in the plenum.

An alternate form of a combustor is one made of permeable sintered metal of which all the walls are, therefore, permeable.

Both forms of combustors form combustion chambers wherein combustion occurs on or near the inner surface of the permeable portions thereof. As a result, combustion is dispersed uniformly over a large area and the entire chamber is available for completion of combustion. Further, the opening in the side of the combustor through which the products discharge is unrestricted for relief of expansion of the products created by combustion in the combustor to minimize turbulent flow.

The nozzle maintains the uniform flow of products delivered from the combustion chamber of the combustor and the secondary combustion chamber which chambers constitute a passage which is constant in cross-section over the axial length of the burner. The products or heating gases are then uniformly converged by the nozzle thereby increasing their velocity and forming a generally laminar stream of heating gases which in the embodiment illustrated is wide and flat.

The burner overcomes the problems of erosion and slowing of the exiting heating gases by use of a metallic combustion chamber and a metallic nozzle. The metallic combustion chamber has eliminated the need for elaborate manifolds through which premix fuel must be fed as ,well as associate diffusing equipment previously needed for distributing the fuel uniformly. Combustion is completed within the combustion chamber eliminating the problems of blow off, incomplete combustion and flame emitting from the burner outlet. Mounting the metallic nozzle on the burner in a manner in which the nozzle is free for expansion minimizes the warping problem. The greater resistance of the metallic nozzle to cyclic conditions greatly increases the life of the burner by minimizing early deterioration of the burner outlet.

Efficiency of the burner and stream emitting therefrom is enhanced by stabilizing the temperature of the nozzle at a high temperature using an insulated shroud and the inspiration of cooling air between the shroud and nozzle.

The resulting basically metallic burner has a higher efficiency than the prior art burners and a greatly increased life over the burners using refractory for combustion chambers and outlets. It produces the required high energy stream or blast for attenuating glass fila ments of a high quality. Simplifying the design of the burner components results in a rugged burner having greater stability and requiring less maintenance thereby reducing production disruptions and shutdowns. The metallic construction reduces the size and weight of the burner.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an elevational view of a burner in accordance with the present invention illustrated as utilized to attenuate glass filaments into fibers;

FIG. 2 is a top view of the burner illustrated in FIG. 1 with a portion thereof cut-away to reveal greater detail;

FIG. 3 is an enlarged sectional view of the burner illustrated in FIG. 2 taken along line 33 thereof;

FIG. 4 is an end view of the burner illustrated in FIG. 2 taken along line 4-4 thereof;

FIG. 5 is a modified form of the nozzle section illustrated in FIG. 3;

FIG. 6 is a full end view of the nozzle section illustrated in FIG. 5; and

FIG. 7 is a fragmentary view of the burner section illustrated in FIG. 3 with a modified form of the combustor and inlet.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to the drawings, FIG. 1 illustrates a burner 10 of the type for generating a high energy stream of products of combustion, or gases, having an inlet 12 for a premix of fuel and air from a supply source not shown. Typical of the premix used would be a mixture of natural gas and air which is burned within the burner 10 and discharged at a high velocity and high temperature from the outlet 14.

In the embodiment illustrated, the gases discharged are used to heat glass filaments l6 aligned along a guide bar 18 and approaching the stream at essentially light angles. As the glass filaments 16, which are solidified glass, pass beyond the bottom of the guide bar 18 sufficient softening occurs so that the blast of heating gases alters the normal path of the filaments 16 to a substantially planar path with the direction of the heating gases. The force of the stream of heating gases reduces the filaments 16 into fine fibers 20 which may be collected on an endless foraminous conveyor, not illustrated, to a felted mat. For high quality fibers 20 with uniform characteristics it has been found that combustion should be completed within the burner 10, that flames should not extend out beyond the outlet 14 and that the flow from the outlet 14 should be generally laminar and uniform.

While the preferred embodiment of the burner illustrated is particularly suited for use in attenuating glass filaments 16, it will be understood that a burner embodying the principles herein disclosed is not limited to use for attenuating glass filaments 16. One skilled in the art would be aware of obvious modifications which could be made, for example, changes to the configurations of the outlet 14, to make the burner suitable for V I other purposes, such as flame hardening or drawing, requiring a high energy stream of products.

Greater detail of the burner 10 is illustrated in FIGS. 2 through 4. FIGS. 2 and 3 illustrate the inlet 12, which typically is a pipe, capped with a plate 22 and having a slot 24 cut within the pipe through which the premix passes in entering a plenum 26 formed by a housing 28 and a combustion housing 30 which will be referred to herein as a combustor. The arrows in FIG. 3 illustrate the general pattern of the flow of premix entering and leaving the plenum 26. The premix passes from the plenum 26 through the permeable surfaces of the combustor 30 into a primary combustion chamber 32.

hi the preferred embodiment illustrated, the combustor 30 has two opposing rectangular permeable surfaces of foraminate sheet material 34 extending between a pair of rectangular end plates 36 and between back plate 38 and flange 40. An indentation in the back plate 38 extends into the primary combustion chamber 32 with a smooth curvature extending over the distance between the end plates 36 to provide for diffusion of the premix issuing from the slot 24 so that the premix is at a uniform pressure at the foraminate sheet surface 34. Premix is preheated within the indentation of the back plate 38 to enhance combustor efficiency. A hole 42 in each end plate 36 allows flow of premix in the indentation past the end plates 36.

The premix permeable surfaces 34 of the combustor are parallel and are spaced according to the burner capacity and the combustion product stream to be developed whereby initial combustion of the premix is generally in parallel planar zones closely adjacent and within the combustor. Further combustion which may approach and even achieve completion occurs in the volume between the initial combustion zones. The outlet from the combustor is of the same area as the cross section of the combustor normal to the surfaces 34 and generally parallel to the back plate 38. This outlet port, therefore, introduces no disruptions in the flow of com- 1 bustion products from the combustor and can be cou- Fabrication of both the combustor 30 and the housing 28 for the plenum is by conventional means such as welding with the material typically being mild steel for the housing 28 and 304 stainless for the combustor 30. An example of one type of the foraminate sheet material 34 used is a product produced under the trademark CONIDURE by National-Standard Company, Carbondale, Pennsylvania, made of 24 gauge 304 stainless sheet having a hole size of 0.012 inches with 8.5 percent open area. A highly rolled form of CONIDURE is used wherein each hole is defined by a generally sharp edged orifice with a diverging profile. The diverging profile faces the combustion chamber 32.

Where desirable, a secondary combustion chamber 44 can be incorporated into the burner 30 to increase the operating flexibility of the burner by widening the range of fuel inputs over which it can be operated. Insulating refractory 46 lines the secondary combustion chamber 44 and is backed by a layer of insulation 48 covering the entire inner periphery of a mild steel casing 50 having front and back flanges 52 and 54, respectively. Assembly of the plenum housing 28 to the secondary combustion chamber casing 50 is accomplished by bolting the back flange 54 to a flange 56 on the plenum housing 28 as at FIG. 2. A gasket 41 seals flanges 54 and 56. One means of mounting the burner is by affixing a nut 60 to the bottom of the casing 50. A fastening screw 64 can be mated with the nut 60 and tightened therein to maintain the burner 10 and base 62 in fixed relation. The base 62 is slidable on a pair of ways 66 one of which is illustrated. Adjustment of the base 62 to move the nozzle tip 14 toward and away from the attenuating zone is accomplished with conventional screw means (not illustrated) bearing against support flange 63. Burner 10 is supported on a cylindrical mount 70 embraced by clamp 68 to which support flange 63 and ways 66 are secured. Alignment of the burner 10 normal to the filaments 16 is accomplished by loosening the clamp 68 from about the cylindrical mount 70 to allow the burner 10 to pivot about the mount 70.

FIGS. 3 and 4 best illustrate a nozzle 72 of the converging type ending in outlet 14 which is a straight throat portion. The outlet configuration of the nozzle 72 is rectangular as best illustrated in FIG. 4. While the nozzle can be a weldment in the particular nozzle illustrated, the walls arev generally of uniform thickness, being cast to three-sixths inch, with the exception of fillets and bosses. The outlet 14 opening is 8% X A inches converging from an inlet opening of 8% X 2 inches. As pointed out above, other configurations could be used particularly where the use is for other then attenuating glass filaments 16. Examples of materials used for the nozzle 72 include lnconel 600 for weldments and Hastaloy and. lnconel 611 for castings. Other materials which may be considered for other uses would be 310 and 309 stainless.

Special attention is given to securing of the nozzle 72 to the burner 10 to allow the nozzle 72 to expand upon being heated by the heating gases passing through the outlet 14. A series of bosses 74 around the periphery of the inlet of the nozzle 72 as illustrated in FIGS. 2 and 3 are provided to allow expansion particularly of the width of the nozzle 72 while at the same time holding the nozzle 72 against the secondary combustion chamber insulating refractory 46 by means of mating stays 76. Leakage between the nozzle 72 and the insulating Shroud is arranged to define cooling ducts 94 to the outer surface of nozzle 72. Its casing 82 is spaced from the nozzle 72 and the plenum flange 56 or downstream face 45 of secondary combustion chamber 44. An inlet port 88 extends across the width of shroud 80 between casing 50 and the rearrnost lip 83 of casing 82 by virtue of the standoff of the shroud from its mounting provided by side extensions 85 as illustrated in FIG.

Cast to the inside periphery of the shroud 80 is an insulating refractory held to the casing 82 by suitable anchors 92, best illustrated in FIG. 3. The insulating refractory 90 above and below the nozzle 72 is formed with a profile terminating slightly beyond the nozzle 72 at the outlet 14 thereof. The profile of the insulating refractory 90 is of a converging nature with respect to the outer surface of the nozzle in the direction of the outlet 14 resulting in cooling air being inspirated into the passages 94 by the heating gases leaving the outlet 14.

Nozzle 72 is centered within shroud 80 by a series of adjustable screws 96, illustrated in FIG. 4, attached to the casing 82 and seating on the outer face of the throat of the outlet 14 of the nozzle 72. Once the screws 96 are properly adjusted, a degree of support is provided for the outlet 14 further tending to stabilize its configuration upon reaching operating temperature.

FIGS. 5 and 6 illustrate a modified form of the nozzle 72 illustrated in FIG. 3, having the addition of cooling fins 98 for increasing the surface area of the nozzle 72 thereby increasing the efficiency of cooling by the air 'drawn into the shroud 80.

FIG. 7 illustrates an alternate combustor 30 having the same configuration as the preferred embodiment, but constructed of sintered powder metal walls 100 of a much heavier thickness than the foraminate sheet material 34. In this alternate, the permeable walls 100 all pass the difiused premix into the combustion chamber 32 from the plenum 26. Other permeable materials could be employed.

The combustors resistance to premix flow in combination with the plenum housing 28 provides for uniform distribution of premix to the combustion chamber 32 by creating a uniform pressure of premix within the plenum resulting in uniform combustion within the combustor 30. In passing through the combustor 30, the premix cools the combustor 30, during continuous operation, so that the combustor 30 is maintained below a temperature which would cause a perceptible color change in the combustor 30 material while combustion is occurring within the combustion chamber 32. Preferably, the combustor 34) will generally follow the shape of the outlet 14 to provide a consistent flow meable surface are of the combustor 30 and its resistance to premix flow and thermal conductivity. Metering of the premix may be accomplished as a function of pressure drop across the combustor by taking appropriate pressure readings.

Once the above conditions have properly been taken into account, combustion occurs within the primary combustion chamber 32 and is completed therein. While it is not known with certainty, it is thought that ignition occurs near the inner surface of the combustor 30 in the form of an infinite number of individual flames having a thin layer of premix between the flame and the surface of the combustor 30. Combustion of the premix is therefore very rapid and spread over a large area resulting in uniform distribution of the products of combustion.

Since the present burner has resulted in a substantial reduction in noise over burners of the prior art, it is also thought that the thin layer may provide a buffer against resonant noise.

In the preferred embodiment of the combustor 30, best illustrated in FIG. 3, the indentation of the back plate 38 has resulted in a substantial heating of the apex of the indentation as has been observed by a glowing of the apex when the burner 30 is in operation. Since the premix is delivered to this isolated hot portion upon entering the plenum 26, the premix is preheated by contact with the back plate 38 before entering the primary combustion chamber 32 further enhancing the rate of combustion.

Characteristics such as preheated fuel, uniform distribution of premix, and a large uniform surface for combustion to uniformly distribute the products of combustion are particularly important in producing a high energy stream of heating gases for attenuating glass filaments 16 into fibers 20. The opposed fuel-air premix permeable planar surfaces of the combustor are believed to provide a broad area for the ignition of the premix and a region in which burning can be completed while avoiding excessive turbulence in the products of combustion. Advantageously, the opposed planar surfaces 34 are parallel. For a high quality fiber product having uniform physical characteristics, combustion should be complete within the burner 10. When the range of premix input required for production exceeds the limits of the primary combustion chamber 32, a secondary chamber 44 is added, as pointed out above, to allow the ignited premix time to complete combustion. The gases produced by complete combustion obtain temperatures hotter than those otherwise produced and the increased temperature increases production efficiency in terms of pounds of glass fiber attenuated per unit volume of fuel. It will be noted that com- I plete combustion also eliminates the possibility of flame emitting from the burner 10. Flames exiting a burner will remelt the fibers formed upon contacting the fibers.

It has been pointed out that the combustion in the primary combustion chamber 32 is rapid, complete, and occurs near the point of entry to the chamber uniformly over a large surface area. As a result of the above characteristics of the combustor 30, the entire volume of the chamber 32 is available for burning and expansion of the products of combustion. The products of heating gases, in the case of the burner 10 illustrated in FIG. 3, are free to travel at a high velocity in a uniform pattern, without abrupt alteration in direction,

through the uniform crosssections of the combustion chambers 32 and 44. Further increases in the velocity of the heating gases are provided by the nozzle 72 which converges the heating gases toward the outlet 14 while maintaining the uniform flow pattern to produce a generally laminar flow stream. Uniformity of the flow pattern is maintained from combustor 30 to outlet 14 resulting in a stream having the temperature and velocity required for attenuating glass filaments.

The nozzle 72 has proven to be stable in its outlet configuration at operating temperature with a minimum of distortion to produce the desired stream of heating gases. The preferred embodiment illustrated was found to maintain its configuration under repeated cycling from ambient to operating temperatures and back to ambient. It appears that cycling has little effect on the life of the nozzle and a life of up to 2 years is expected.

The increase in life for the nozzle 72 above is also expected of the combustor 30 because of the low operating temperature of the combustor 30.

The combination of the combustor 30 and nozzle 72, absent the secondary combustion chamber 44 where flexibility in the range of input isnt needed, results in an all metal burner which can produce the required high energy stream for attenuating glass filaments.

It has been found that the burner 10 of the preferred embodiment produces a greater amount of glass fiber than the prior art burners for a given amount of fuel consumed as indicated by a 5 percent savings in fuel consumption for a similar production of fibers 20. It is therefore concluded that there is a higher operating efficiency for the present burner 10.

The present burner 10 is one constructed basically of metal which operates satisfactorily to produce the high energy stream of heating gases with the required force to attenuate glass filaments of high quality and accomplishes this result with greater efficiency. A longer life can be expected of the burner 10 due to the greater stability of the metallic components over the prior art refractory components with the metallic components reducing burner size and weight. Operation of the burner 10 is cooler with respect to personnel due to the lower operating temperature of the combustor 30 and the shroud around the nozzle 72. There is a simplification of design in the present burner 10 resulting in a greater ruggedness and this along with the greater stability in the combustor 30. and nozzle 72 results in longer life for higher line production and less down time.

The principle and mode of operation of the apparatus have been explained and what is considered to be its best embodiment has been illustrated and described. It should however be understood that the invention may be practical otherwise than as specifically illustrated and described without departing from its spirit or scope.

I claim:

1. Burner apparatus for burning a fuel-air mixture comprising:

a. a metallic housing having at least two opposing fuel-air mixture permeable surfaces defining walls of a combustion chamber, said permeable surfaces having openings located therein to disperse combustion of the fuel-air mixture over said surfaces, said chamber having an outlet port;

b. a plenum chamber encompassing at least said permeable surfaces and exposing said outlet port to the exterior of said combustion chamber;

c. means to supply the fuel-air mixture to said plenum for passage through said permeable surfaces for combustion within said metallic housing, said outlet port passing the combustion products from said housing; and,

d. means for dispersing said fuel-air mixture in said plenum chamber.

2. Burner apparatus as defined in claim 1 wherein said fuel-air mixture permeable surfaces are of a sintered powder metal construction.

3. Burner apparatus as defined in claim 1 wherein said surfaces are perforated plates.

4. Burner apparatus as defined in claim 1 wherein said surfaces are rectangular.

5. Burner apparatus as defined in claim 1 wherein said surfaces are parallel and planar.

6. Burner apparatus as defined in claim 1 including a pair of end plates extending between the ends of said surfaces and a back plate extending between the sides of said surfaces opposite said outlet port, said plates and surfaces forming said metallic housing.

7. Burner apparatus as defined in claim 6 wherein said means for dispersing said fuel-air mixture is said back plate which is indented toward the inside of said metallic housing to provide a flow guide for dispersing the fuel-air mixture in said plenum.

8. Burner apparatus as defined in claim 7 wherein said indented back plate is extended sufficiently into said housing to heat the apex thereof whereby the fuelair mixture contacting the apex is preheated prior to entering said metallic housing.

9. Burner apparatus as defined in claim 8 wherein said means for supplying fuel-air mixture includes a conduit having an aperture facing and adjacent said indented back plate.

10. Burner apparatus as defined in claim 3 wherein said perforated plates have perforations about twelve thousandths of an inch across and constituting about eight and one half per cent of the plate areas.

11. Burner apparatus as defined in claim 2 wherein said fuel-air mixture permeable surfaces exhibit suflicient resistance to flow of said fuel-air mixture through said surfaces to effect the dispersion of said fuel-air mixture in said plenum chamber.

12. Burner apparatus for burning a fuel-air mixture comprising:

a. a metallic housing having at least two opposing fuel-air mixture permeable surfaces defining wall portions of a combustion chamber, said penneable surfaces having openings located therein to disperse combustion of the fuel-air mixture over said surfaces, said chamber having an outlet port to the exterior of said chamber;

b. a plenum chamber encompassing at least said permeable surfaces and exposing said outlet port to the exterior of said chamber;

c. a metallic nozzle communicating with said outlet 60 e. means for dispersing said fuel-air mixture in said plenum chamber. 13. Burner apparatus as defined in claim 12 wherein said nozzle includes at least two converging sides.

14. Burner apparatus as defined in claim 12 wherein said nozzle includes an outlet, said outlet having a rectangular cross section.

15. Burner apparatus as defined in claim 12 including a refractory chamber intermediate said metallic housing and said nozzle.

16. Burner apparatus as defined in claim 15 wherein said refi'actory chamber has a cross section normal to the flow of products therethrough conforming to the outlet port for said metallic housing.

17. The combination defined in claim 12 including cooling fins on the exterior of said nozzle.

18. Burner apparatus as defined in claim 12 including a shroud for said nozzle to shield the surroundings of said nozzle from heat radiating therefrom.

19. Burner apparatus as defined in claim 18 wherein said shroud includes a refractory liner.

20. Burner apparatus defined in claim 19 wherein said refractory liner includes surfaces spaced from said nozzle and having converging profiles with respect to said nozzle to define ducts having outlet ports adjacent the nozzle outlet port whereby the flow of combustion products from said nozzle inspirates cooling air through said ducts and over the exterior of said nozzle.

21. Burner apparatus as defined in claim 18 including means maintaining said shroud spaced from said nozzle to define a duct for cooling fluid, and cooling fins extending from said nozzle into said duct.

22. Burnerapparatus as defined in claim 18 wherein said nozzle includes an outlet having a rectangular cross section, and said shroud includes stays for mounting said nozzle to said burner to establish the position of said nozzle with respect to the axial direction of said burner while allowing expansion of said nozzle in the direction parallel to the width of its rectangular outlet and normal to the axial direction of said burner.

23. Burner apparatus for burning a fuel-air mixture comprising:

a. a metallic housing having a fuel-air mixture permeable surface defining a wall portion of a combustion chamber, said chamber having an outlet port to the exterior of said chamber;

b. a plenum chamber encompassing at least said permeable surface and exposing said outlet port to the exterior of said chamber;

c. a metallic nozzle communicating with said outlet port in said metallic housing, said nozzle including an outlet having a rectangular cross section;

d. a shroud for said nozzle to shield the surroundings of said nozzle from heat radiating therefrom, said shroud including stays for mounting said nozzle with respect to the axial direction of said burner while allowing expansion of said nozzle in the direction parallel to the width of its rectangularoutsaidnozzle.

a: a a w 

1. Burner apparatus for burning a fuel-air mixture comprising: a. a metallic housing having at least two opposing fuel-air mixture permeable surfaces defining walls of a combustion chamber, said permeable surfaces having openings located therein to disperse combusTion of the fuel-air mixture over said surfaces, said chamber having an outlet port; b. a plenum chamber encompassing at least said permeable surfaces and exposing said outlet port to the exterior of said combustion chamber; c. means to supply the fuel-air mixture to said plenum for passage through said permeable surfaces for combustion within said metallic housing, said outlet port passing the combustion products from said housing; and, d. means for dispersing said fuel-air mixture in said plenum chamber.
 2. Burner apparatus as defined in claim 1 wherein said fuel-air mixture permeable surfaces are of a sintered powder metal construction.
 3. Burner apparatus as defined in claim 1 wherein said surfaces are perforated plates.
 4. Burner apparatus as defined in claim 1 wherein said surfaces are rectangular.
 5. Burner apparatus as defined in claim 1 wherein said surfaces are parallel and planar.
 6. Burner apparatus as defined in claim 1 including a pair of end plates extending between the ends of said surfaces and a back plate extending between the sides of said surfaces opposite said outlet port, said plates and surfaces forming said metallic housing.
 7. Burner apparatus as defined in claim 6 wherein said means for dispersing said fuel-air mixture is said back plate which is indented toward the inside of said metallic housing to provide a flow guide for dispersing the fuel-air mixture in said plenum.
 8. Burner apparatus as defined in claim 7 wherein said indented back plate is extended sufficiently into said housing to heat the apex thereof whereby the fuel-air mixture contacting the apex is preheated prior to entering said metallic housing.
 9. Burner apparatus as defined in claim 8 wherein said means for supplying fuel-air mixture includes a conduit having an aperture facing and adjacent said indented back plate.
 10. Burner apparatus as defined in claim 3 wherein said perforated plates have perforations about twelve thousandths of an inch across and constituting about eight and one half per cent of the plate areas.
 11. Burner apparatus as defined in claim 2 wherein said fuel-air mixture permeable surfaces exhibit sufficient resistance to flow of said fuel-air mixture through said surfaces to effect the dispersion of said fuel-air mixture in said plenum chamber.
 12. Burner apparatus for burning a fuel-air mixture comprising: a. a metallic housing having at least two opposing fuel-air mixture permeable surfaces defining wall portions of a combustion chamber, said permeable surfaces having openings located therein to disperse combustion of the fuel-air mixture over said surfaces, said chamber having an outlet port to the exterior of said chamber; b. a plenum chamber encompassing at least said permeable surfaces and exposing said outlet port to the exterior of said chamber; c. a metallic nozzle communicating with said outlet port in said metallic housing; d. means to supply a fuel-air mixture to said plenum for passage through said permeable wall portions of said metallic housing for combustion within said metallic housing, said outlet port passing the combustion products from said housing and through said nozzle; and e. means for dispersing said fuel-air mixture in said plenum chamber.
 13. Burner apparatus as defined in claim 12 wherein said nozzle includes at least two converging sides.
 14. Burner apparatus as defined in claim 12 wherein said nozzle includes an outlet, said outlet having a rectangular cross section.
 15. Burner apparatus as defined in claim 12 including a refractory chamber intermediate said metallic housing and said nozzle.
 16. Burner apparatus as defined in claim 15 wherein said refractory chamber has a cross section normal to the flow of products therethrough conforming to the outlet port for said metallic housing.
 17. The combination defined in claim 12 including cooling fins on the exterior of said nozzle.
 18. Burner apparatus as defined in claim 12 including a Shroud for said nozzle to shield the surroundings of said nozzle from heat radiating therefrom.
 19. Burner apparatus as defined in claim 18 wherein said shroud includes a refractory liner.
 20. Burner apparatus defined in claim 19 wherein said refractory liner includes surfaces spaced from said nozzle and having converging profiles with respect to said nozzle to define ducts having outlet ports adjacent the nozzle outlet port whereby the flow of combustion products from said nozzle inspirates cooling air through said ducts and over the exterior of said nozzle.
 21. Burner apparatus as defined in claim 18 including means maintaining said shroud spaced from said nozzle to define a duct for cooling fluid, and cooling fins extending from said nozzle into said duct.
 22. Burner apparatus as defined in claim 18 wherein said nozzle includes an outlet having a rectangular cross section, and said shroud includes stays for mounting said nozzle to said burner to establish the position of said nozzle with respect to the axial direction of said burner while allowing expansion of said nozzle in the direction parallel to the width of its rectangular outlet and normal to the axial direction of said burner.
 23. Burner apparatus for burning a fuel-air mixture comprising: a. a metallic housing having a fuel-air mixture permeable surface defining a wall portion of a combustion chamber, said chamber having an outlet port to the exterior of said chamber; b. a plenum chamber encompassing at least said permeable surface and exposing said outlet port to the exterior of said chamber; c. a metallic nozzle communicating with said outlet port in said metallic housing, said nozzle including an outlet having a rectangular cross section; d. a shroud for said nozzle to shield the surroundings of said nozzle from heat radiating therefrom, said shroud including stays for mounting said nozzle with respect to the axial direction of said burner while allowing expansion of said nozzle in the direction parallel to the width of its rectangular outlet and normal to the axial direction of said burner; and e. means to supply a fuel-air mixture to said plenum for passage through said permeable wall portion of said metallic housing for combustion within said metallic housing, said outlet port passing the combustion products from said housing and through said nozzle. 